Quadruple perovskite materials with high Curie temperatures and their preparation methods

Abstract

This invention provides a tetrafold perovskite material with a high Curie temperature, the chemical formula of which is LaCu3Fe2Re2O. 12 Furthermore, in the aforementioned tetrap perovskite material, 5%-8% of the Fe atoms are in a disordered state; the Curie temperature of the tetrap perovskite material is 1000 K. This invention also provides a method for preparing the tetrap perovskite material with a high Curie temperature as described herein. The tetrap perovskite material of this invention has a high ferromagnetic phase transition temperature, with a Curie temperature of 1000 K. The Curie temperature of the tetrap perovskite material of this invention is currently the highest among oxide material systems with intrinsic ferromagnetism. Due to its extremely high Curie temperature, the tetrap perovskite material LaCu3Fe2Re2O of this invention... 12 It can be used as a magnetic material and has broad application prospects in fields such as magnetic storage and advanced spintronic devices.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis. Specifically, this invention relates to a tetrafold perovskite material with a high Curie temperature and its preparation method. Background Technology

[0002] In modern society, ferromagnetic materials are the foundation of many functional materials, widely used in information, energy, machinery, military, and aerospace fields. Currently, magnetic materials have a vast market, generating billions of dollars in market value annually. The Curie temperature of a magnetic material directly determines its application temperature range and is one of its most critical performance parameters. On the other hand, perovskite oxides, due to their unique structure and ionic combinations, exhibit rich and interesting physical properties, such as high-temperature superconductivity, colossal magnetoresistance, magnetoelectric multiferroic properties, and half-metallicity, making them one of the most studied material systems in the condensed matter physics field. Particularly noteworthy is the development of a tetratonic perovskite ACu3B2B′2O with simultaneous ordering at both A and B sites. 12 Due to Cu 2+ The introduction of ions greatly enhances Cu 2+ -B,Cu 2+ The magnetic coupling strength between -B′ and BB′ is significant, hence these materials typically have very high Curie temperatures, such as CaCu3Fe2Re2O. 12 and CaCu3Fe2Os2O 12 These materials exhibit Curie temperatures of 560K and 580K, respectively. To further increase the Curie temperature of such materials, electronic doping of the A-site to increase the magnetic coupling strength between different ions within the material is an effective method, as illustrated in patent application number 202010494194.0, which describes CaCu3Fe2Re2O. 12 Ca 2+ La ions 3+ Ion substitution yielded a tetrap perovskite material, LaCu3Fe2Re2O, with a Curie temperature as high as 620 K. 12 .

[0003] As mentioned above, whether it is Cu 2+ Whether it's ion doping or electronic doping, both methods aim to increase the Curie temperature of a material by controlling the A-site ions. However, there are currently few examples of using the B-site to control the Curie temperature of materials.

[0004] Generally, the Curie temperature of a material is controlled by adjusting the degree of order of the ions at the B sites. Currently, existing technologies typically increase the Curie temperature by adjusting the B sites from a disordered state to an ordered state. For example, in B-site ordered double perovskite Sr2FeMoO6, as the degree of disorder at the B sites gradually increases from 8% to 15%, the corresponding Curie temperature decreases from 405 K to 375 K (see reference: BJPark et al, J. Magn. Magn. Mater. 1851, 272-276 (2004)).

[0005] However, the existing technologies mentioned above do not significantly improve the Curie temperature. Therefore, there is an urgent need for a method that can significantly increase the Curie temperature. Summary of the Invention

[0006] Therefore, one object of the present invention is to provide a tetrap perovskite material having the highest Curie temperature among intrinsically ferromagnetic and ferrimagnetic materials. Another object of the present invention is to provide a method for preparing the tetrap perovskite material of the present invention.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0008] On the one hand, the present invention provides a tetrafold perovskite material with a high Curie temperature, the chemical formula of which is LaCu3Fe2Re2O. 12 Furthermore, in the tetrad perovskite material, 5%-8% of all Fe atoms are in a disordered state; the Curie temperature of the tetrad perovskite material is 1000K.

[0009] The inventors of this application unexpectedly discovered that if the degree of order of Fe in the tetrahedral perovskite material decreases (i.e. becomes disordered, such as Fe being enriched together instead of being uniformly distributed in the material), the Curie temperature of the material will be significantly increased, such as to 1000K.

[0010] Preferably, in the tetrap perovskite material with a high Curie temperature described in this invention, the space group of the tetrap perovskite material is Pn-3, and the lattice constant is .

[0011] On the other hand, the present invention provides a method for preparing the quadruple perovskite material with a high Curie temperature, comprising the following steps:

[0012] (1) La2O3, CuO, Fe2O3, Re powder and Re2O7 were ground and mixed in a molar ratio of 7:42:14:10:9 in a protective gas environment to obtain a mixture;

[0013] (2) After sealing and packaging the mixture, it is then synthesized;

[0014] (3) Cool the synthesized product to room temperature and depressurize it to obtain the precursor;

[0015] (4) Place the precursor under a pressure P less than or equal to 10. -5 In a vacuum quartz tube of Pa;

[0016] (5) Then, the quartz tube is heated to 400-600℃ and held for 5-60 minutes for post-treatment, and then cooled to room temperature to obtain a quadruple perovskite material with a high Curie temperature.

[0017] The inventors of this application unexpectedly discovered that the Curie temperature of tetrahedral perovskite materials can be significantly increased through the high-temperature post-treatment in a high-vacuum environment described in this application. This is likely due to the fact that the post-treatment of this invention reduces the order of Fe atoms in the material, leading to a significant increase in the Curie temperature. Furthermore, the inventors of this application also unexpectedly discovered that high-temperature treatment in a high-vacuum environment, contrary to the teachings of the prior art, does not increase the order of the material, but rather reduces the order of the tetrahedral perovskite material. On the other hand, the reduction in the B-site order of the tetrahedral perovskite material, contrary to the teachings of the prior art, does not decrease the Curie temperature, but rather results in a significant increase in the Curie temperature (approximately 300°C), which originates from the Fe atoms at the B-site. 3+ The enrichment of ions resulted in higher strength Fe 3+ -O-Fe 3+ Magnetic coupling is what allows for a significant increase in the Curie temperature of the post-processed quadruple perovskite material.

[0018] In this invention, there is no particular limitation on the temperature used for post-processing. If it is below 100°C, the degree of order of the sample will remain unchanged and the physical properties will not change. If it is above 800°C, the sample will lose oxygen and the sample quality will drop sharply.

[0019] In this invention, there is no particular limitation on the time used for post-processing. If it is less than 5 minutes, the orderliness of the sample will not change much. If it is more than 60 minutes, the orderliness of the sample will remain in a relatively stable state without change.

[0020] In this invention, there is no particular limitation on the post-processing pressure, but it is preferable that the pressure P is less than or equal to 10. -5 In a vacuum environment of Pa. If the pressure is greater than 10 Pa. -5 Pa can make the sample more prone to deterioration.

[0021] Preferably, in the method described in this invention, the pressure P in step (4) is greater than or equal to 10. -7 Pa.

[0022] Preferably, in the method described in this invention, in step (5), the heating is carried out at a heating rate of 2-4 °C / min.

[0023] Preferably, in the method described in this invention, in step (5), the cooling to room temperature is carried out at a cooling rate of 1-3 °C / min.

[0024] Preferably, in the method described in this invention, the grinding in step (1) is carried out in a mortar for 30 minutes to 3 hours, preferably 1 to 2 hours.

[0025] Preferably, in the method described in this invention, the particle size of the mixture in step (1) is 100 to 5000 mesh, more preferably 200 to 1000 mesh.

[0026] Preferably, in the method described in this invention, the sealing and wrapping in step (2) is performed using a gold capsule or a platinum capsule.

[0027] Preferably, in the method described in this invention, the thickness of the gold capsule or platinum capsule is 0.02 to 0.2 mm.

[0028] Preferably, in the method described in this invention, the synthesis in step (2) is carried out under the following conditions: temperature of 900-1150°C, pressure of 8-10 GPa, and time of 10 minutes or more, preferably 10-120 minutes.

[0029] Preferably, in the method described in this invention, the protective gas is one or more of nitrogen, helium, and argon.

[0030] Preferably, in the method described in this invention, the synthesis in step (2) is carried out in a six-sided top press or a 6-8 type two-stage push press.

[0031] Preferably, in the method described in this invention, the cooling to room temperature in step (3) takes less than or equal to 15 seconds or 2 to 10 hours.

[0032] According to the method provided by the present invention, in step (1), grinding can not only make the materials uniformly mixed, but also reduce the particle size of each material, and the reduction of the particle size of the materials is conducive to their uniform mixing. In the present invention, the particle size of the mixture after grinding is generally in the micrometer range.

[0033] The present invention has the following beneficial effects:

[0034] The tetrad perovskite material LaCu3Fe2Re2O of the present invention 12It exhibits a high ferromagnetic phase transition temperature, with a Curie temperature of 1000K. The Curie temperature of the tetragonal perovskite material of this invention is the highest among oxide materials with intrinsic ferromagnetism to date, and it has potential applications in future advanced electronic devices. Furthermore, the tetragonal perovskite material LaCu3Fe2Re2O of this invention... 12 It has a large saturation magnetization (up to 8.5 μ). B Due to its extremely high Curie temperature, the tetragonal perovskite material LaCu3Fe2Re2O of this invention... 12 It can be used as a magnetic material and has broad application prospects in fields such as magnetic storage and advanced spintronic devices. Attached Figure Description

[0035] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0036] Figure 1 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III) and the quadruple perovskite material LaCu3Fe2Re2O of Example 2 of the present invention 12 The magnetic susceptibility curve of (No. II) as a function of temperature; where ZFC represents zero-field cooling and FC represents field cooling.

[0037] Figure 2 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), Example 2: Quadruple Perovskite Material LaCu3Fe2Re2O 12 (Item II) and the tetrad perovskite material LaCu3Fe2Re2O in Comparative Example 1 12 (I) Curves showing the variation of magnetization intensity with magnetic field strength at different temperatures.

[0038] Figure 3 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), Example 2: Quadruple Perovskite Material LaCu3Fe2Re2O 12 (Item II) and the tetrad perovskite material LaCu3Fe2Re2O in Comparative Example 1 12 XRD pattern of (number I).

[0039] Figure 4 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), and the tetrad perovskite material LaCu3Fe2Re2O compared to Comparative Example 1. 12 The distribution diagram of different elements (number I); among them, Figure 4 A-4F is the quadruple perovskite material LaCu3Fe2Re2O from Example 1 of this invention. 12 (Number III) Distribution diagram of different elements Figure 4 G-4L is the tetrad perovskite material LaCu3Fe2Re2O used in Comparative Example 1. 12 The distribution of different elements in (I) is shown in the figure.

[0040] Figure 5 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), and the tetrad perovskite material LaCu3Fe2Re2O compared to Comparative Example 1. 12 Comparison of absorption spectra (number I). Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0042] Comparative Example 1

[0043] The comparative example is actually Embodiment 1 from patent application number 202010494194.0. The specific method includes the following steps:

[0044] La₂O₃, Fe₂O₃, Re₂O₇, CuO, and Re powders with a purity higher than 99.9% were mixed in a molar ratio of 7:14:9:42:10 and ground in an argon-filled glove box for 2 hours to obtain a mixture with a particle size of 200 mesh. The mixture was then filled and sealed in gold capsules with a wall thickness of 0.1 mm. The gold capsules were placed in a six-sided press and reacted with the raw materials inside for 30 minutes at a pressure of 8 GPa and a temperature of 1000 °C to obtain the reaction product. After cooling to room temperature within 15 seconds, the pressure was slowly released, and finally the reaction product was removed from the gold capsules to obtain LaCu₃Fe₂Re₂O₇. 12 , numbered I.

[0045] Example 1

[0046] The above sample I was placed in a high vacuum (P=10). -5 The material was prepared by heating a quartz tube containing Pa to 500°C, placing the tube in a muffle furnace, raising the temperature to 500°C at a rate of 2°C per minute, holding it at that temperature for 10 minutes, and then cooling it to room temperature at a rate of 2°C per minute. This process yielded a tetrahedral perovskite material LaCu3Fe2Re2O with a high Curie temperature. 12 , numbered III.

[0047] Example 2

[0048] The above sample I was placed in a high vacuum (P=10). -7 The material was prepared by heating a quartz tube containing Pa to 600°C, placing the tube in a muffle furnace, heating it to 600°C at a rate of 4°C per minute, holding it at that temperature for 60 minutes, and then cooling it to room temperature at a rate of 3°C per minute. This process yielded a tetrahedral perovskite material LaCu3Fe2Re2O with a high Curie temperature. 12 , numbered II.

[0049] Performance testing

[0050] 1. XRD Test

[0051] The structure of the half-metal was characterized using an X-ray diffractometer manufactured by Huber GmbH, Germany. A copper target was used for X-ray generation, and a single-crystal monochromator was used to remove stray light, preserving the Cu-K matrix. α1 Monochromatic light (wavelength 0.15046 nm) was used, and the test was conducted under normal temperature and pressure conditions, with a diffraction angle 2θ ranging from 10 to 100 degrees.

[0052] Reference Figure 3 , Figure 3 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), Example 2: Quadruple Perovskite Material LaCu3Fe2Re2O 12 (Item II) and the tetrad perovskite material LaCu3Fe2Re2O in Comparative Example 1 12 XRD pattern of (number I). Figure 3 B and 3C show the position and intensity of each diffraction peak. Figure 3 B and 3C show the LaCu3Fe2Re2O prepared in Examples 1 (III) and 2 (II). 12 It has a cubic perovskite structure, belongs to the Pn-3 space group, and has a lattice constant of approximately 0.5. The structural parameters of samples II and III were obtained through structural refinement, and detailed data are shown in Table 1. Table 1 shows that the disorder degree of sample II is 5%, and that of sample III is 8%. BVS was calculated using the formula V... i =∑ j S ij and S ij =exp[(r0-r ij [0.37], where Cu 2+ r0 is 1.679, Fe 3+ The value of r0 is 1.759.

[0053] Table 1: Structural refinement results of Sample II and Sample III

[0054]

[0055]

[0056] 2. Magnetic susceptibility and testing

[0057] The magnetic property measurement system (MPMS) from Quantum Design, Inc. (USA) was used to measure the change in magnetic susceptibility of the half-metal with temperature. Zero-field cooling (ZFC) was used without an external magnetic field; once the temperature dropped to 2K, a 0.1 Tesla magnetic field was applied, and the test temperature range was increased from 2K to 1000K. Field cooling (FC) was used with a 0.1 Tesla magnetic field applied, and the test temperature range was decreased from 1000K to 2K. The temperature rise and fall rates were 2K per minute.

[0058] Reference Figure 1 , Figure 1 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III) and the quadruple perovskite material LaCu3Fe2Re2O of Example 2 of the present invention 12 The magnetic susceptibility versus temperature curve (number II); where ZFC represents zero-field cooling and FC represents field-cooled cooling. Figure 1 As shown, the LaCu3Fe2Re2O prepared in Examples 1(III) and 2(II) 12 It exhibits strong ferrimagnetic properties and a very high Curie temperature (1000 K). In contrast, the Curie temperature of Comparative Example 1, sample I without post-treatment, is only 620 K.

[0059] 3. Magnetization test

[0060] The magnetization of the half-metal was measured using a Magnetic Property Measurement System (MPMS) from Quantum Design, Inc. at 900 K, 800 K, 700 K, 300 K, 150 K, 100 K, and 2 K. At each temperature, the applied magnetic field was increased from 0 T to 7 T, then decreased to -7 T, and finally increased back to 7 T. The rate of change of the applied magnetic field was 0.02 T per second.

[0061] Refer to 2, Figure 2The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), Example 2: Quadruple Perovskite Material LaCu3Fe2Re2O 12 (Item II) and the tetrad perovskite material LaCu3Fe2Re2O in Comparative Example 1 12 (I) Curves showing the variation of magnetization intensity with magnetic field strength at different temperatures. Figure 2 A-2D shows the LaCu3Fe2Re2O prepared in Examples 1(III) and 2(II) at a temperature of 2K. 12 The saturation magnetization of the sample is approximately 8.5 μm. B / fu indicates that LaCu3Fe2Re2O 12 It has a high saturation magnetization.

[0062] 4. Element distribution test

[0063] The elemental distribution of annealed and unannealed samples was obtained using scanning tunneling electron microscopy energy-dispersive spectroscopy. Specifically, Figure 4 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), and the tetrad perovskite material LaCu3Fe2Re2O compared to Comparative Example 1. 12 The distribution diagram of different elements (number I); among them, Figure 4 A-4F is the quadruple perovskite material LaCu3Fe2Re2O from Example 1 of this invention. 12 (Number III) Distribution diagram of different elements Figure 4 G-4L is the tetrad perovskite material LaCu3Fe2Re2O used in Comparative Example 1. 12 The distribution of different elements in (I) is shown in the figure. Figure 4 B-4F represents the distribution of La, Cu, Fe, Re, and O elements in annealed sample (III). Figure 4 B-4F shows enrichment of Fe and Re elements. Figure 4 H-4L represents the distribution of La, Cu, Fe, Re, and O elements in the unannealed sample (I). Figure 4 The H-4L sample has a uniform elemental distribution. Therefore, combined with Fe... 3+ -O-Fe 3+ The strong magnetic coupling between them suggests that the enrichment of Fe element is induced by LaCu3Fe2Re2O 12 The reasons for the rise in Curie temperature.

[0064] 5. Absorption spectroscopy test

[0065] Cu and Fe in L2,3 The absorption spectra of Re at the L3 edge were measured at room temperature. Similarly, the absorption spectrum of Re at the L3 edge was also measured at room temperature. All three elements were measured using TEY mode.

[0066] Reference Figure 5 , Figure 5 The tetrad perovskite material LaCu3Fe2Re2O of Example 1 of this invention 12 (Number III), and the tetrad perovskite material LaCu3Fe2Re2O compared to Comparative Example 1. 12 Comparison of absorption spectra (number I). Figure 5 The LaCu3Fe2Re2O prepared in Example 1(III) is shown. 12 By examining the valence states, it can be observed that the valence states of the materials before annealing (I) and after annealing (III) did not change significantly.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a quadruple perovskite material with high Curie temperature, comprising the following steps: (1) grinding and mixing La2O3, CuO, Fe2O3, Re powder and Re2O7 in a molar ratio of 7:42:14:10:9 in a protective gas environment to obtain a mixture; (2) after the mixture is sealed and wrapped, performing synthesis; (3) cooling the synthesis product to room temperature and unloading pressure, thereby obtaining a precursor; (4) placing the precursor in a vacuum quartz tube at a pressure P less than or equal to 10 -5 Pa; (5) then, heating the quartz tube to 400-600℃ and keeping for 5-60 minutes for post-treatment, and then cooling to room temperature to obtain a quadruple perovskite material with high Curie temperature; The quadruple perovskite material with high Curie temperature has a chemical formula of LaCu3Fe2Re2O 12 and in the quadruple perovskite material, 5%-8% of Fe atoms among all Fe atoms are in a disordered state in terms of atom number. The quadruple perovskite material has a Curie temperature of 1000 K.

2. The method of claim 1, wherein, The quadruple perovskite material has a space group of Pn−3 and a lattice constant of 7.489 Å.

3. The method of claim 1, wherein, The pressure P in the step (4) is greater than or equal to 10 -7 Pa.

4. The method of claim 1, wherein, In step (5), the heating is performed at a heating rate of 2-4℃ / min.

5. The method of claim 1, wherein, In step (5), the cooling to room temperature is performed at a cooling rate of 1-3℃ / min.

6. The method of claim 1, wherein, The grinding in step (1) is performed in a mortar for 30 minutes to 3 hours.

7. The method of claim 6, wherein, The grinding in step (1) is performed in a mortar for 1-2 hours.

8. The method of claim 1, wherein, The particle size of the mixture in step (1) is 100-5000 mesh.

9. The method of claim 8, wherein, The particle size of the mixture in step (1) is 200-1000 mesh.

10. The method of claim 1, wherein, The sealing and wrapping in step (2) is performed by using a gold capsule or a platinum-gold capsule.

11. The method of claim 10, wherein, The thickness of the gold capsule or the platinum-gold capsule is 0.02-0.2 mm.

12. The method of claim 1, wherein, The synthesis in step (2) is performed under the following conditions: temperature of 900-1150℃, pressure of 8-10 GPa, and time of 10 minutes or more.

13. The method of claim 12, wherein, The synthesis in step (2) is performed under the following conditions: temperature of 900-1150℃, pressure of 8-10 GPa, and time of 10-120 minutes.

14. The method of claim 1, wherein, The protective gas is one or more of nitrogen, helium and argon.

15. The method of claim 1, wherein, The synthesis in step (2) is performed in a hexagonal top press or a 6-8 type secondary propulsion press.

16. The method of claim 1, wherein, The cooling to room temperature in step (3) is completed in less than or equal to 15 seconds or 2-10 hours.

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